The present invention relates very generally to transducers and pertains, more particularly, to a unitary piezoelectric-magnostrictive transducer in which magnetostrictive and electrostrictive/piezoelectric transducer effects are combined together to form an improved transducer design.
Either electrostrictive (piezoelectric) transducers or magnetostrictive transducers have been used in the past as the transduction means for generating or receiving sound in underwater acoustic systems. However, although these different types of transducers have been used separately, the art does not teach the combination of active electrostrictive and magnetostrictive transducer materials intimately combined in a unitary transducer construction. It is the concepts of the present invention that teach the embodying of the transducer in this unitary construction. Such a combination of transducer effects is used to attain special directional patterns such as in the form of a cardioid. Also, this arrangement allows the possibility of using one transducer to electrically tune the other.
In the past the piezoelectric ceramics, such as lead zirconate titanate were nearly twice as active as the magnetostrictive materials. However, there is now an advent of newer rare earth iron magnetostrictive materials that are comparable to the piezoelectric ceramics and this has the effect of enhancing the transducer combination effects of the present invention.
In accordance with the present invention, rare earth iron magnetostrictive materials such as Tb.sub.3 Dy.sub.7 Fe.sub.2 or the amorphous metalic glass magnetostrictive material such as Fe.sub.81 B.sub.13.5 Si.sub.3.5 C.sub.2 may be used as the magnetostrictive portion of the transducer. This makes the activities of both transducer mechanisms much more compatible leading to better performance when both effects are combined as in accordance with this invention. In accordance with the invention, the two effects are combined mechanically so as to in essence form a single transducer thus greatly improving performance. Although the aforementioned active materials may be employed such as the new rare earth iron magnetostrictive materials, it is understood that the prior less active materials may also be used in accordance with the principles of this invention with only possibly somewhat reduced performance.